Effect of the Structure of Amido-polynitrogen Molecules on the Complexation of Actinides

The complexation and solvent extraction of Eu(III) and actinides in different oxidation states (Am(III), Pu(IV), Np(V)) by bitopic molecules with a dipyridyl-phenanthroline cycle as nitrogen unit and one or two amido functions are described. The complexation has been studied in methanol-water solution with hydrophilic molecules to enhance knowledge about this new family of ligands and to identify the most interesting structural effect. Some extraction tests have been performed with lipophilic molecules of the family to check the possible utility of the new class of ligands under representative fuel reprocessing conditions. These first studies have demonstrated that the presence of a preorganized N-donors unit like dipyridyl-phenanthroline improves the ligand's affinity for actinides and its An/Ln selectivity.     

Novel Polyurethane Gels: The Effect of Structure on Gelation

Novel polyurethane gels have been reported in common solvent like dimethyl formamide (DMF). Polyurethanes have been synthesized from diisocyanates, diols and rigid chain extenders. We have illustrated the influence of chemical structure of the chain extenders on gelation rate, thermal property and morphology of the gels in DMF. Gelation rate increases significantly with the rigidity of the chain extender. Introduction of more rigid chain extender molecules in polyurethane prepolymer enhanced the thermal stability of the pure polymer. On the contrary, the solvent retention power of the gels gradually decreases with increasing rigidity of chain extender presumably because of the poor dispersion/greater aggregation of the hard segments in the soft segment matrix. Morphology and formation of gelation have been discussed.     

水分子对金属有机骨架材料结构及性能的影响

金属有机骨架材料(Metal-Organic Frameworks, MOFs)是一种新型有机-无机杂化材料,其在气体的吸附分离、催化、磁学、生物医学等领域表现出诱人的应用前景.但是,在水分子存在的情况下MOFs结构及性能会受到很大的影响,极大的阻碍了其工业化进程.本文系统介绍了水分子对MOFs结构的破坏机理,并从金属和配体两方面总结了在水分子存在的情况下MOFs的稳定性问题;阐述了水分子的吸附机理以及吸附水分子后MOFs性能的变化;并且对水分子影响问题的研究趋势做了展望,以期为今后的研究提供参考.     

水分子对金属有机骨架材料结构及性能的影响

金属有机骨架材料(Metal-Organic Frameworks,MOFs)是一种新型有机-无机杂化材料,其在气体的吸附分离、催化、磁学、生物医学等领域表现出诱人的应用前景。但是,在水分子存在的情况下MOFs结构及性能会受到很大的影响,极大的阻碍了其工业化进程。本文系统介绍了水分子对MOFs结构的破坏机理,并从金属和配体两方面总结了在水分子存在的情况下MOFs的稳定性问题;阐述了水分子的吸附机理以及吸附水分子后MOFs性能的变化;并且对水分子影响问题的研究趋势做了展望,以期为今后的研究提供参考。     

超临界二氧化碳中聚氨酯吸附小分子的影响因素

研究了超临界ＣＯ２中降压时间以及小分子的溶度参数、亲电性和芳香性等因素对聚氨酯吸附小分子的影响,考察了小分子比蒸发速率对小分子在聚氨酯中解吸的影响。结果表明聚氨酯易于吸附亲电性试剂和多数芳香剂族小分子,通常比蒸发速率大的小分子在聚氨酯中解吸也快。     

Chemical Recycling and Liquefaction of Rigid Polyurethane Foam Wastes through Microwave Assisted Glycolysis Process

Glycolysis of polyurethane rigid foams (PUFs) was performed utilizing microwave irradiation at atmospheric pressure. The effects of various metal hydroxide and acetate catalysts as well as different microwave powers were investigated. All reactions were monitored by FTIR spectroscopy. The recovered liquid product containing OH functional groups was applied as a portion of the polyol in formulation of a new polyurethane rigid foam product. The reactivity factors and densities were compared with the foam produced from totally virgin polyol.     

超临界二氧化碳中聚氨酯对小分子的吸附作用

研究了超临界ＣＯ２中聚氨酯对乙醇、麝香草酚和β－苯乙醇等小分子的吸附作用,观测了超临界ＣＯ２的温度、压力、吸附时间和聚氨酯厚度对小分子吸附量的影响以及小分子在聚氨酯中的释放规律,并探讨了小分子的渗透机理。     

气味分子的结构理论

人和动物通过嗅觉可以感受到各种不同的气味。嗅觉是有挥发性的气味分子通过嗅觉器官,刺激嗅神经而产生的感觉。     

软段结构对聚氨酯性能影响的研究

用熔融缩聚法俣成了己二酸系和己二酸／芳香二酸混合系两个系列的聚酯；同溶液一步法将部分聚酯与ＭＤＩ反应，形成一系列聚酯型氨酯，以化学分析，ＶＰＯ，ＩＲ，ＤＳＣ，ＷＡＸＤ，力学拉伸等手段对聚酯和聚氨酯进行了表征；讨论了软段聚酯的结构对聚氨酯的结晶性，耐热性，粘结性等性能的影响。     

软段对水性聚氨酯结构与性能的影响

以低聚物多元醇、异氟尔酮二异氰酸酯(IPDI)、亲水单体二羟甲基丙酸(DMPA),乙二胺为主要原料,制备了一组不同组成的聚氨酯乳液。通过粘度测定、粒度分析、力学性能和耐水性能测试、原子力显微镜(AFM)分析,研究了软段类型、软段分子量对乳液及其胶膜性能的影响。结果表明,分子结构规整、易结晶的软段合成的聚氨酯树脂力学性能和耐水性能都较好,对聚己二酸酯而言,分子量减小,其合成的水性聚氨酯拉伸强度提高,耐水性能却有很大程度的下降。     

Structure and Dynamics of Chiral Molecules

Could there be chiral methane? What is the characteristic structural feature (in a physicochemical sense) of a molecule? This question dates back to Louis Pasteur, the discoverer of molecular chirality, and since the work of van't Hoff and Le Bel is generally considered by chemists as solved. In the present article it is pointed out that there exist fundamentally conflicting theoretical views of the physical origin of molecular chirality. These views predict consequences that could, in principle, be distinguished experimentally, but at present there is no conclusive experimental evidence available. Possible experiments are suggested that test different hypotheses. The importance of the magnitude of the parity-violating energy difference δE_PV in molecules due to the weak nuclear force for both the structure and spectra of chiral molecules and for the kinetics of racemization is discussed. The chemical relaxation rate coefficient of chiral molecules with some appreciable energy of excitation is derived for several limiting cases of a simple statistical mechanical model, which takes ΔE_PV into account.     

Effect of Laser-Induced Optical Breakdown on the Structure of Bsa Molecules in Aqueous Solutions: An Optical Study

The influence of laser radiation of a typical surgical laser on the physicochemical properties of the Bovine Serum Albumin (BSA) protein was studied. It was established that the physicochemical characteristics of optical breakdown weakly depend on the concentration of protein molecules. At the same time, the patterns observed for an aqueous solution of BSA irradiated with a laser for different time periods were extremely similar to the classical ones. It was established that after exposure to laser radiation, the optical density of protein solutions increases. At the same time, the intensity of BSA fluorescence due to aromatic amino acid residues decreases insignificantly after exposure to laser radiation. In this case, the position of the excitation and emission maximum does not change, and the shape of the fluorescence spot on 3D maps also does not change significantly. On the Raman spectrum after exposure to laser radiation, a significant decrease in 1570 cm⁻¹ was observed, which indicates the degradation of α-helices and, as a result, partial denaturation of BSA molecules. Partial denaturation did not significantly change the total area of protein molecules, since the refractive index of solutions did not change significantly. However, in BSA solutions, after exposure to laser radiation, the viscosity increased, and the pseudoplasticity of aqueous solutions decreased. In this case, there was no massive damage to the polypeptide chain; on the contrary, when exposed to optical breakdown, intense aggregation was observed, while aggregates with a size of 400 nm or more appeared in the solution. Thus, under the action of optical breakdown induced by laser radiation in a BSA solution, the processes of partial denaturation and aggregation prevail, aromatic amino acid residues are damaged to a lesser extent, and fragmentation of protein molecules is not observed.     

有机共轭分子电子结构的计算

根据分子结构的共振理论,为PPP方法选择了一套合理的经验参数。应用CNDO/2方法和PPP方法计算了有机共轭分子的电子能级、最低三重态激发能及增感染料分子的半波电位。     

Consequences of Strain for the Structure of Aliphatic Molecules

The chemist is accustomed to deriving structures and preferred conformations of organic compounds from rigid molecular models and standard values for bond lengths, bond angles, and torsional profiles. In the case of strained compounds, this rigid structural model has to be abandoned and replaced by a flexible one which takes individual conditions of strain into consideration. It is shown, on the basis of new experimental structure data, that the force field method is suitable and highly reliable for the calculation of structural parameters and preferred conformations of strained compounds. It is, therefore, capable of replacing the rigid molecular model. Furthermore, the systematic analysis of strain induced angle and bond deformation gives a new pivot for the development of a qualitative discussion of deformation in strained molecules and hence for improved conformational analysis. — In the course of this work we were able to isolate two rotamers of D,L -3,4-di(1-adamantyl)-2,2,5,5-tetramethylhexane; this is the first isolation of a rotamer pair of an aliphatic hydrocarbon.     

Thermal Aging Effect on Mechanical Properties of Polyurethane

This study concerns the effect of thermal aging on mechanical properties of polyurethane. Polyurethane samples were exposed at 85° and 120°C under inert atmosphere. Mechanical tests were carried out on these samples the aging period. Tensile tests were performed to see the effect of aging on elastic modulus (E), stress (σ_r), and strain (?_r) at break. It was shown that there are two distinct periods. Due to aging, E and σ_r increase in the first period, then they decrease in the second period. ?_r decreases first and then increases. Fatigue tests were performed on unaged and aged samples. It was shown that the fatigue behavior of polyurethane (PU) is improved the same way during the first stage of aging. In the second step, the number of cycles to failure increases due to aging. The results show that aging has an important effect on mechanical properties of PU. The strain at break decreases during the first step of aging due to post-cross-linking and then increases due to chain scission in the network. Based on these results, the effect of cross-linking and chain scission on the mechanical properties of PU was discussed.     

润滑剂对聚氨酯弹性体的反增塑效应

聚氨酯嵌段聚合物的硬链段易于聚集形成微晶相分散于软链段连续相中,原位组成橡塑合金使聚氨酸弹性体兼具高模量、高动态力学性能、高耐磨性等性质,但是决定这些性质的软、硬段形态结构强烈地受组成和制备工艺的影响,使聚合物具有优良的综合性能并不简单．影响软、硬段...     

基于Diels-Alder反应的自修复聚氨酯的结构与修复行为

采用呋喃封端的聚氨酯预聚体与双马来酰亚胺反应,合成了基于Diels-Alder(DA)反应的热可逆自修复聚氨酯(PU-DA).利用FTIR、DSC和gel-solution-gel方法对其分子结构、热性能及其可逆性进行了表征,结果表明,具有热可逆性的DA键被成功引入到聚氨酯中,从而赋予聚氨酯具有良好的再加工性能和自修复性能.通过偏光显微镜观测对材料的自修复行为进行了考察,结果表明,由于DA反应的热可逆性,0.5 mm深度划痕的聚氨酯试样在120℃热处理300 s或130℃热处理150 s后划痕便可消失,从而实现了划痕的自修复.并且模拟实际生活中聚合物材料受到轻微损伤时的情况,通过拉伸试验对0.5 mm深度划痕有效自修复的热处理温度和时间进行了确定,并对同一受损部位多次刻划-修复的修复效率进行了详细研究,结果表明:在120℃处理15 min可达到最佳修复效果,其一次修复效率可达71%,同一受损部位经过3次刻划—修复后,其修复效率仍能达到35%.